Removal of Ruthenium from Aqueous Solution by Clinoptilolite

Abstract

Ruthenium compounds are highly toxic and carcinogenic. In the present study, clinoptilolite was used in the removal of Ru species from aqueous solutions. Clinoptilolite is a good choice of sorbents because it is naturally abundant and therefore cheap. After the process where Ru was removed from the aqueous solution, the clinoptilolite was characterized by X-ray diffraction, X-ray fluorescence, thermogravimetric analysis, and Fourier-transform infrared spectroscopy techniques. The influence of pH, contact time, and temperature on the adsorption of Ru was investigated and the optimum conditions were found to be 2 h of contact time and pH = 2. Pseudo first-order, pseudo second-order, Elovich, and intra-particle diffusion models were used to analyze the adsorption-rate data. The pseudo second-order model was found to be the best kinetics model in terms of matching the experimental results obtained. Adsorption isotherms were constructed to assess the maximum adsorption capacity of clinoptilolite. The Langmuir model fitted the data reasonably well in terms of regression coefficients. Adsorption studies were also performed at different temperatures to calculate the thermodynamic parameters. The numerical value of DG 0 decreased with increasing temperature, indicating that adsorption is favored at higher temperatures. The positive values of DH 0 corresponded to the endothermic nature of the adsorption processes. The proposed method of removal is applicable at an industrial scale.

Graphene Oxide as an Adsorbent for Ruthenium from Aqueous Solution

“…The adsorption of ruthenium (III) on graphene oxide is mainly attributed due to electrostatic attraction between the negative surface of graphene oxide bearing oxygen functional groups and ruthenium (III) ion and coordination of ruthenium (III) with oxygen atom. The attachment of hydroxyl group into ruthenium (III) coordination sphere reduces the interaction between ruthenium (III) and graphene oxide bearing surface negative charge on oxygen atom beyond pH 2 [31] …”

“…The attachment of hydroxyl group into ruthenium (III) coordination sphere reduces the interaction between ChemistrySelect ruthenium (III) and graphene oxide bearing surface negative charge on oxygen atom beyond pH 2. [31] To investigate the effect of ionic strength, adsorption experiments were carried out with NaCl and MgCl 2 in the concentration range of 0.01-0.1 M. Figure 4 depicts the plot of adsorption capacity of ruthenium (III) on GO as a function of ionic strength. Experimental results revealed that, in case of NaCl, adsorption capacity decreases gradually with increase in NaCl concentration up to 0.07 M, beyond which it is independent of ionic strength.…”